The presence of dust and dirt on cinematographic films is a considerable problem in that it impairs the projected image and can lead to scratching of the film during transport through a projector. Various methods have been considered for removal of dust and dirt from films and perhaps the simplest idea would be to attempt to simply blow particles from the film. However, this is not satisfactory as electrostatic attraction of particles to cinematographic films makes it difficult to shift such particles. If a continuous jet of air is directed at the surface of a film an air boundary layer very close to the film surface is formed and this creates a downward pressure causing particles to cling to the film surface. The smaller the particles, the greater is the hold on the surface. The higher the velocity of air used the more pressure is exerted in or by the boundary layer making small particles apparently immovable. Accordingly such an arrangement will not work satisfactorily and will not remove grease.
In current cinematographic Film Cleaners. Film is cleaned by ultrasonic vibration of the film as it is passed through a bath containing a volatile hot liquid. The ultrasonics are generated electronically, and physically coupled from a transducer via the liquid in the bath, causing vibration of the Film which removes dust, dirt and grease by surface cavitation. the Film is then passed through a drying tower which evaporates the liquid and dries the Film. However, this drying process limits the cleaning speed of the film to approximately 200 feet per minute with current solvents and is expensive due to the solvent costs. Furthermore, the solvent most commonly used in the film cleaning process is Trichloreoethane--a CFC--which is being phased out from January 1994.
The present invention seeks to provide an alternative film cleaning apparatus and method which provides significant advantages over existing film cleaners.